A World Health Organization study concludes that serious mental health disorders are common globally, and go largely untreated in developing countries.

Investigators found that 75 to 85 percent of people with serious cases of mental disorder in developing countries went without treatment in the 12 months preceding the interviews, while 35 to 50 percent went untreated in developed countries.

But the study found that severe cases, a small percentage of cases overall, were more likely to be treated than moderate or mild cases of mental disorder.

The study suggests reallocating treatment resources could help ensure treatment for the more serious illnesses, while preventing less serious ones from progressing into serious cases.

The results of the WHO study, published in the Journal of the American Medical Association, were based on more than 60,000, face-to-face interviews, conducted between 2001 and 2003, in eight developed countries and six less-developed countries. Among the nations surveyed were the United States, China, India, Ukraine, Indonesia, Nigeria, and Brazil.

Investigators found the percentage of people suffering from a severe mental disorder ranged from four-percent in Shanghai to more than 26 percent in the United States as a whole.

Ronald Kessler is a professor of population studies at the Harvard University School of Health Care Policy in Massachusetts. "When you put all these things together, about one out of every four Americans has a mental disorder, at some time in their life, something in the range of 9 to 20 percent for most countries," said Professor Kessler.

Researchers say they do not know whether openness in the United States makes people feel more at ease talking about mental health issues, and whether that accounts for the United States leading the world in almost every category of mental illness.

Conversely, the authors believe a fear of questioners resulted in an undercount of people suffering from major mental health conditions in developing countries.

"This is the first time anybody has ever done a survey," he said. "They have never heard of such a thing as a survey. So, we had to an awful lot of work, going through churches and community organizations, and so forth, explaining what this was about, having traditional healers come with us and so forth, to try to do the best we could to piece together an understanding and an appreciation of what the enterprise was. But we realize that in some countries still, the numbers we have here are underestimates."

One country where serious mental health illnesses may be underestimated is China, which reports the lowest depression rate in the world, at roughly two percent. At the same time, Mr. Kessler says "China has, by far, the highest suicide rates in the world. It makes no sense that the [depression] rates are this low," he said.

Professor Kessler says Ukraine leads the world in substance abuse. "For those of you who are familiar with the situation in Ukraine will know that there is a tremendous problem with alcoholism," he said. "With the break-up of the Soviet Union, the mortality rate is extraordinary for alcohol problems, particularly among men."

The authors of the study conclude that a higher priority ought to be given to treatment, not only to help the seriously mentally ill, but those with less serious mental conditions, to keep them from progressing to severe mental illness.